The meteor is thought to have been about 20 metres wide before it blew up in the atmosphere. Collectors and researchers have recovered a number of fragments in Chelyabinsk, including a large one found at the bottom of a lake, allowing geologists to learn more about its origins.

"No other process can be considered to cause such melting after a meteoroid is formed," says Shin Ozawa of Tohoku University in Sendai, Japan.

High pressure

Ozawa and his colleagues examined some of the recovered fragments and found a particular form of the mineral jadeite that seems to have been formed by rapid crystallisation. This would require pressures of between 3 and 12 gigapascals and temperatures of 1700-2000 ºC. From that, they could calculate properties of the impacting body – it was likely to have been between 150 and 190 metres wide and travelling at anything from 1400 to 5400 kilometres an hour.

"The size and velocity of the impactor seem to be consistent with those of impacts in the main asteroid belt," says Ozawa, meaning it was not a freak event that sent Chelyabinsk hurtling our way.

It is also possible that the meteor is one of many siblings formed in the impact, so other large chunks could still be lurking out there. "In some cases, fragments of asteroids formed by an impact can have similar orbits," says Ozawa.

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Fragments from the Chelyabinsk meteorite have revealed that it was formed in an impact 290 million years ago (Image: Butsenko Anton/ITAR-TASS Photo/Corbis)